jgmurray

I am currently looking to purchase a '96 993 coupe. One of the cars that I am looking at is cosmetically very clean although the mileage is a bit high (50K). The records show that the car was very well maintained. The current owner mentioned that he had the engine pulled and disassembled for cleaning due to carbon buildup in the valves and pistons. In the dealership where he had the work done he was shown several other cars which were receiving the same servicing. He stated that it was a $6,000. repair covered by Porsche. Has anyone else heard of this problem?

Anir

That's the first time I've heard of such a thing, although my 993 has only 11,000 miles.

It is my understanding that regular use of products such as Lubro Moly Ventil Sauber and Jectron (or Techron, etc) does a good job of preventing deposits. I use a can of both Lubro Moly products prior to each oil change (about q 5-6K).

There is an interesting engine cleaning system marketed by MotorVac Technologies in Orange, CA, that has proven quite successful in diesel fleets, and is also available for passenger cars (I used to own their stock). It seems to be a useful, very inexpensive means of cleaning deposits. I estimate it would cost only $50 - 200 for a treatment.

Having to disassemble the engine at a cost of $6,000 sounds more extreme than I would have expected, even in cars that were not treated regularly with the aforementioned products.

Rohan Nath

50k for a 993 is not very high mileage and a $ 6k engine teardown appears odd. My car has close to 30k miles and I am unaware of any engine work coming up due to carbon buildup.

The fact that the $ 6k repair was covered by Porsche also raises a red flag. I cannot imagine Porsche paying for a routine maintenance item.

This appears to be an issue specific to that vehicle. I would we very careful.

Darryl

I have heard that if you drive short distances most of the time, carbon starts to build and there is a chance of plugs to be fouled. Short distance cannot be measured but I'm guessing 5-10 miles under 15-20 minutes. The engine and oil doesn't have time to warm up to 180 degrees. I was advised that a previous owner did not take his 993 out for long drives enough and hence there was problems. I now take my car for 2 hour drives even if I have to drive around the island twice.

Terry Adams

I saw carbon buildup at 110K miles on the piston heads of my '87 Carrera when I had the top end rebuilt due to worn valve guides letting oil in. The rebuild was $6K also. I cannot imagine any Porsche, let alone a 993, needing the kind of work you describe at such low mileage. I use a bottle of Techron just before every 5K oil change. In the current weak economy there are too many nice 993s available to bother with one that has a suspect history. If Porsche covered the alleged repair, the seller should have a record of it.

os993

Just for a point of reference, my 95 992 with 85K miles is not only clean on the outside, but purrs like a kitten inside. Engine leaks no oil, clutch is still original, and I've seen no engine problems whatsoever.

Previous owner (I bought car at 60k miles) drove car daily for highway commuting. No carbon issues observed. I drive my 993 daily as well, and make sure to rev the engine up (when properly warmed up) as often as possible (what a difficult thing to do...sacrifices, sacrifices... )

Also, to some contrary beliefs, I track the car on occassion, and think this helps more than it hinders our beauties, assuming proper maintenence and care is taken

Lastly, as Terry mentioned, with the economy the way it is, you have good in purchasing a good 993 without a questionable past. Don't settle Good luck and let us know what you do.

Steve Weiner-Rennsport Systems

JG:

First, I would tell you that carbon buildup is normal for unleaded fuels and performing a
$ 6K de-carbonization service is more than just questionable. The MTBE and other compounds in unleaded gasolines creates soft carbon deposits on the backs of the intake valves and at the injector tips which cause rough idling, stumbling and overall drivability problems. Short city trips and insufficient higher RPM running exacerbates these problems and will make the car feel pretty "doggy".

Fuel treatments such as LubroMoly Jectron & Ventil Sauber or Chevron's Techron go a long way at removing and preventing these deposits and will restore the performance to all but the "problem children".

As Anir mentioned, a process called MotorVac can be used to treat the worst of these problems and we have had good success with that machine. Its a shop procedure, not a D-I-Y'er.

Let me share a short story,.......

Many cars with a few miles on them can fail emissions testing for excessive HC. This is not uncommon at all and a compression test will show less-than-new figures that would suggest the need for a valve job to clean up the carbon that has accumulated and created leaky valves. This is one of the main causes of HC failures at the Smog Test Station.

Many shops and Dealer service departments will use the results of the compression tests to sell and perform a valve job to cure the "problem", and help the car pass the Smog test. Its a great profit center.
We started using MotorVac about 5 years ago after a demo showed the same improvement in compression tests that the valve job did on these otherwise healthy engines. After MotorVac, these cars all passed HC testing with no problem and the compression was almost normal, as long as there were no other issues like worn guides.

Then, we tried using high-dosage treatments of LubroMoly or Techron to see if this might do the same thing in cars that would not pass the HC part of the test; same result in most cases. Of course, we changed the oil immediately following a double blast of these chemical treatments and then took the car to the Smog Testing Station.

My point is that many shops and Dealerships oversell their services to show a bigger profit and the vast majority of people have no idea that they might have been sold something that wasn't necessary. After all, the Service Manager can hide behind the compression test and offer a good sound case that these procedures are needed. When no other other alternatives are offered especially if the car has low or moderate mileage, it can become a conflict of interest IMHO, and a classic case of placing profit above the interests of the customer.

In this case, I'd offer that the Dealership has discovered a new profit center and it would appear that they are doing their damndest to make money, at the expense of their customer's financial well-being.

We do the LubroMoly thing here first, and then MotorVac, if necessary. Valve jobs and decarbonization are only performed when the guides must be replaced or if somebody bends a valve from missing a shift,......

My advice when faced with a recommendation for such services, would be to try some bottles of LubroMoly or Techron first, then explore the other alternatives. Spending that kind of money on a 50K motor, even if it needed new guides, seems excessive to me.

Just one man's take on these situations,....

Viken

Steve,

Was the oil changed for the sole purpose of passing smog or is it necessary to do so after each Jectron/Ventil Sauber or Techron treatment?

TIA

cecil

This is happening all over. The local dealer here has done this to several cars. There is probably a bulletin out on it. Here is what is happening. there are some small holes the smog pump uses to pump extra air to keep the engine from running rich prior to being warmed up. They are getting clogged with carbon causing a check engine light. I know this seems hard to believe but the Porsche fix is to tear down the engine and clean out the carbon. I run a bottle of Techron through every 5,000 miles and at 54,000 haven't had a light, of course I removed the stinken bulb when I installed the supercharger This would be a really big deal if Porsche were still making these cars. The full weight of the Feds fall on those who run a little rich on start up.

Mark from Phoenix

I agree with Cecil above. I recently bought a 96 with 50k miles that had the same issue because the previous owner lived close to work and the car was used as a daily driver. The local dealer said it was common on cars driven short distances and the fix was to clean the small tubes to the smog pump and then basically perform a valve job to clean the carbon off. The symptom is that the check engine light comes on. There is usually no other symptoms. The dealer mentioned that my particular car had no other probs and was well maintained. I have put 10k more miles and have had zero probs. I wouldn't worry too much about this if it's the only thing wrong and the owner has all service records.

Ray Calvo

The carbon buildup is news to me; I thought that the use of unleaded fuel had negated the need to "decoke the cylinder heads". When my '84 Carrera was apart at 120K miles, no hint of carbon problems. Then again, when I took it out I invariably would drive it for a 2-3 hour wringout thru the Allegheny Mountains. Also, it got a Techron treatment about every year. The 993 is being treated similarly; no hint of problems at 62K miles.

Glad to hear that giving a car an "Italian tuneup" still has merits - even on a smog-equipped 993!

cecil

Ray, the small holes to the smog pump are the problem. When they clog they cause the check engine light. The dealers just clean everything while they are in there. Without OBDII and the smog pump there would be no problem, even then it would seem if you drive "hard" and use a good fuel system cleaner you can avoid the light, or you can just "break" the bulb.

vinrey

I've had this problem happen twice on my 96 993c2. I think i first appeared at 65k and around 80k. Each time it was carbon buildup clogging those tiny holes--sorry, I'm not too mechanically inclined. The first time it cost about $600 to declog using Techron products--one bank was cleaned. The second time the other bank needed cleaning but they cleaned the other bank for good measure this time. Again $600. They did tell me as you all did that I needed to rev the car more and treat with Techron. The light came on again at 97k but this was not the problem this time. The idle just needed adjusting. I've had no problems since high revving the car and enjoying the heck out of it. Thanks for your help.

Vince

Allen

Is this Techron you guys are talking about the Techron Fuel System Cleaner? I have always heard that no additives were necessary and that they were a waste of money...is that not true? Mine has 31K miles and is driven ~1 hour pretty hard every 2 weeks or so...do I need to use some of this Techron?

becker - 97'C4S

I had the check engine light and I think I might have the similar problem I just got the Chevron additive and I'm about to put it in as soon as my tank goes low.

I've been told that it could also be the auxiliary air valve (towards the back of the engine) that might've rusted.

BTW I've been giving it consistent "italian tuning" as I had the rev-limiter kicking in several times at track events.